The long-term objective is to make it possible to repair tooth defects by applying solutions and then composite materials which will bond to the surface. When composites can be durably bonded to both dentin and enamel by adhesion, the amount of "drilling" (and therefore the need for local anesthetics) will be lessened, because there will no longer be the necessity to cut away vital supportive dentin to make undercuts and mechanically lock the filling material in place. A recent breakthrough in this project suggests that this goal is a real possibility. The specific aims of the project are to determine the essential mechanisms of the new bonding method and to optimize variables in its materials and methods. The work plan is to characterize the surface modification of dentin and enamel which results from the application of the aqueous ferric oxalate (or alternative) mordant solution. This microstructure will be detailed with scanning and transmission electron microscopies, and the components determined by X-ray, secondary ion mass spectroscopy, and other techniques. The role played by N-phenylglycine will be revealed by functional comparisons of chemically related alternatives. The surface interpenetration by the polar difunctional monomer of this system will be characterized by transmission electron microscopy. The methodology will include the use of ultraviolet, infrared, and electron-spin resonance spectroscopies. Once the source and nature of the polymerization are known for the present system, it will then become possible to make substitutions for the various components, broaden the scope of the capability, and facilitate the transfer of this technology to clinical usefulness. Success will improve treatments of cervical and root lesions as well as repairs of tooth crowns, and it will become possible to provide protective coatings of exposed root surfaces where there has been gingival recession.